low oil pressure DODGE TRUCK 1993 Service Repair Manual

0 - 2
LUBRICATION
AND
MAINTENANCE

• Commercial service
When a vehicle is continuously subjected to severe
driving conditions, lubricate:
• Body components
• All the driveline coupling joints
• Steering linkage More often than normal driving conditions

DUSTY
AREAS
With this type of severe driving condition, special
care should be given to the:
• Engine air cleaner filter
• PCV filter
• Crankcase ventilation system
• Brake booster control valve air filter. Verify that the filters and the associated compo­
nents are clean. Also verify that they are functioning
effectively. This will minimize the amount of abra­ sive particles that enter the engine.

OFF-ROAD
(4WD)
OPERATION
After off-road (4WD) operation, inspect the under­
side of the vehicle. Inspect the:
• Tires
• Body structure
• Steering components
• Suspension components • Exhaust system
• Threaded fasteners

HARSH
SURFACE ENVIRONMENTS
After extended operation in harsh environments,
the brake drums, brake linings, and rear wheel bear­ ings should be inspected and cleaned. This will pre­
vent wear and erratic brake action.

ROUTINE MAINTENANCE
The following routine maintenance is recommended
on a monthly basis: TIRES—Inspect the tires for unusual wear/damage.
Determine if the inflation pressure is adequate for
the vehicle load. BATTERY—Inspect and clean the terminals.
Tighten the terminals if necessary. FLUIDS—Determine if the component fluid levels
are acceptable. Add fluid, if necessary. LIGHTS/ELECTRICAL—Test all the electrical sys­
tems in the vehicle for proper operation. It is also recommended that the engine oil and the
washer fluid level be determined at each fuel fill-up.

VEHICLE
NOISE CONTROL
Vehicles with a GVWR of 4 535 kg (10,000 lbs), or
more, are required to comply with Federal Exterior Noise Regulations (Fig. 2).
VEHICLE
NOISE
EMISSION
CONTROL INFORMATION

DATE
OF
VEHICLE
MANUFACTURE

THIS
VEHICLE CONFORMS
TO
U.S. EPA REGULATIONS FOR NOISE EMISSION

APPLICABLE
TO
MEDIUM
AND HEAVY
DUTY
TRUCKS. THE
FOLLOWING
ACTS OR THE CAUSING THEREOF BY ANY PERSON ARE PROHIBITED BY THE NOISE CONTROL ACT
OF 1972. (A) THE
REMOVAL
OR

RENDERING
INOPERATIVE, OTHER
THAN
FOR
PURPOSES
OF
MAINTENANCE,
REPAIR.
OR REPLACEMENT, OF ANY NOISE CONTROL DEVICE OR ELEMENT OF
DESIGN
(LISTED
IN
THE
OWNERS
MANUAL)
INCORPORATED
INTO
THIS
VEHICLE
IN COMPLIANCE
WITH
THE NOISE CONTROL
ACT:
(B) THE
USE
OF
THIS
VEHICLE
AFTER SUCH DEVICE
OR
ELEMENT
OF
DESIGN HAS BEEN REMOVED
OR
RENDERED
INOPERATIVE.

PU626D

Fig.
2 Vehicle
Noise
Emission
Control Information
Label

UNAUTHORIZED
DEFEAT
OF
NOISE
CONTROL COMPONENTS
Federal law prohibits removal, altering or other­
wise defeating any noise control component. This in­
cludes before or after the vehicle is in use. Federal
law also prohibits the use of a vehicle after a noise
control component is defeated.

REQUIRED MAINTENANCE/SERVICE
FOR
NOISE
CONTROL

The following maintenance is required after each
6-month or 9 600 km (6,000 miles) interval. This will
ensure that the vehicle noise control components are
operating properly.

EXHAUST SYSTEM
Inspect exhaust system for exhaust leaks and dam­
aged components. The exhaust hangers, clamps and
U-bolts should be attached and in good condition.
Burned or ruptured mufflers, damaged exhaust pipes should be replaced. Refer to Group 11—Exhaust Sys­
tem/Intake Manifold for service information.

AIR
FILTER
HOUSING/CANISTER
Inspect the air filter assembly for proper fit. Verify
the cover is securely attached to the housing/canis­
ter. Inspect all the air filter housing hoses for con­ nections. The gasket between the air filter housing and throttle body must be in good condition. The air
filter element should be clean and serviced according
to the maintenance schedule.

FUEL
REQUIREMENTS
GASOLINE
ENGINES
All engines require the use of unleaded gasoline to
reduce the effects of lead to the environment. Also unleaded fuel is necessary to prevent damage to the
catalytic converter/02 sensor. The fuel must have a
minimum octane rating of 87 based on the (R + M)/2
calculation method.

•

LUBRICATION
AND
MAINTENANCE
0 - 15
DIESEL
ENGINES

The Diesel engine oil level indicator is located at
the left center of the engine, above the
fuel
injection

pump (Fig. 3).

Fig.
3
Diesel
Engine
Oil
Dipstick

ACCEPTABLE
OIL
LEVEL
To maintain proper lubrication of an engine, the
engine oil must be maintained at an acceptable level.
For gasoline engines, the acceptable levels are indi­ cated between the ADD and
FULL
marks on oil
dip­
stick. For Diesel engines, the acceptable levels are
indicated between the L (low) and H
(high) marks
on
oil dipstick. The oil level should be checked periodically. The
vehicle should be on a level surface. Wait for
five
minutes after stopping the engine. For gasoline en­
gines,
add oil only when the level indicated on the
dipstick is at or below the ADD mark. For Diesel en­
gines,
add oil only when the level indicated on the
dipstick is between the L and H marks.
Never oper­
ate a Diesel
engine when
the oil
level
is below
the L mark. The distance between the L and H
marks represents 1.9L (2 Qts) engine oil.

CAUTION:
Do not
overfill
an
engine crankcase
with

oil. This
will
cause
oil
aeration
and
result
in a de­

crease
in the
engine
oil
pressure.
ENGINE
OIL
CHANGE AND FILTER REPLACEMENT

WARNING: PROTECTIVE CLOTHING
AND
GLOVES SHOULD
BE
WORN. EXPOSED SKIN SHOULD
BE

WASHED
WITH
SOAP
AND
WATER
TO
REMOVE
USED
ENGINE
OIL.
DO NOT
USE
GASOLINE, THIN­
NER,
OR
SOLVENTS
TO
REMOVE ENGINE
OIL

FROM
SKIN.
DO NOT
POLLUTE. DISPOSE
OF
USED
ENGINE
OIL
PROPERLY.
ENGINE
OIL
FILTER

All engines are equipped with a throw-away type
oil filter. The same type of filter is recommended
when the filter is changed.

OIL CHANGE
AND
FILTER
REPLACEMENT
Bring engine up to normal operating temperature.
A more complete drainage of oil will result.
(1) Remove the drain hole plug and drain the en­
gine oil from the crankcase.
(2) Install the drain hole plug with a replacement
gasket. For gasoline engines, the oil filter should be
replaced during every second engine oil change.
For Diesel engines, the oil filter should be re­
placed during every engine oil change.
(3) Rotate the oil filter counterclockwise to remove
it.
(4) Clean the engine cylinder block oil filter boss. (5) Apply a light coat of new engine oil to the rub­
ber seal on the oil filter.
(6) Install and hand tighten the oil filter 1/2 to 3/4
of a turn clockwise. (7) Add new engine oil at the fill hole location on
top of the engine cylinder head cover. Wipe off any spilled oil.
(8) Observe the oil level on the dipstick.

CAUTION:
Do not
overfill
the
engine crankcase
with

oil.
(9)
Start the engine. Observe the oil pressure
gauge or warning lamp (as applicable). If the oil
pressure does not increase, stop the engine immedi­ ately. Check oil level.

COOLING SYSTEM

WARNING:
USE
EXTREME CAUTION WHEN
THE
ENGINE
IS
OPERATING.
DO NOT PUT
YOUR
HANDS NEAR
THE
DRIVE BELT(S), PULLEYS
OR
FAN BLADE.
DO NOT
STAND
IN A
DIRECT LINE
WITH
THE FAN
BLADE.

INSPECTION SCHEDULE
Determine the coolant level. Inspect the cooling
system hoses/clamps after each service interval has
elapsed.

COOLANT LEVEL
It is recommended that the engine coolant level be
inspected at least once a month during periods of hot
weather.
With the engine at normal operating temperature,
check the coolant level in the coolant reserve tank.
The coolant level must be at least above the ADD mark. Add coolant to the coolant reserve tank only.

0-18
LUBRICATION
AND
MAINTENANCE

•
COOLANT FREEZE PROTECTION

Cooling systems contain a 50/50 mixture of anti­
freeze (ethylene glycol) and distilled water. This is
the recommended coolant mixture.
It is recommended that the degree of coolant pro­
tection be tested every 12 months. If the coolant is
contaminated or rusty, the cooling system should be
drained, flushed. Refill with a 50/50 mixture of fresh
coolant. Refer to Group 7—Cooling Systems for addi­
tional information.

SYSTEM
INSPECTION

WARNING:
IF THE
ENGINE
HAS
BEEN RECENTLY
OPERATED,
DO NOT
REMOVE
THE
RADIATOR

CAP.
THIS WILL AVOID
YOU
BEING SCALDED

WITH
HOT, PRESSURIZED COOLANT.

(1) Test the radiator cap for proper sealing and op­
eration. Use caution when removing the radiator cap
to avoid contact with hot coolant. Place a heavy rag
or towel over the cap and turn to the first stop. Do
not press down. Pause to allow the pressure to re­
lease through the overflow tube. Then press down
and turn counterclockwise to remove the cap.
(2) Inspect the coolant overflow tubing and the
connections at the coolant reserve tank and at the
radiator.
(3) Inspect the entire cooling system for leaks. A
black-light detector can be used as an aid in detect­ ing the source of coolant leaks.
(4) Inspect the radiator and air conditioner con­
denser fins for debris, etc. (5) If necessary, refer to Group 7—Cooling Systems
for additional information and service procedures.

RADIATOR CAP
The radiator cap must be completely tightened to
provide proper pressure. Inspect and test radiator cap
when cooling system service is performed.

MAIN,
FLUSH
AND
FILL

WARNING: ANTI-FREEZE (ETHYLENE GLYCOL)
IS
POISONOUS.
KEEP
OUT OF THE
REACH
OF
CHIL­

DREN.

Drain, flush, and fill the cooling system at the in­
terval specified in maintenance schedule. For proper service instructions see Group 7, Cooling System.

HOSES AND
FITTINGS
It is recommended that rubber hoses be periodi­
cally inspected. Inspect all hose fittings for looseness and corrosion.
ENGINE
AIR
CLEANER
FILTER
ELEMENT

MAINTENANCE
SCHEDULE
With normal driving conditions, the engine air
cleaner filter element should be replaced:
• Light-Duty Cycle-after each 48 000 km (30,000
miles) interval has elapsed
• Heavy-Duty Cycle-after
each
38 000 km (24,000
miles) interval has elapsed
When the vehicle is operated in dusty areas, the
filter element should be replaced more often.
For Diesel engines, the air filter canister should be
cleaned at the same time the filter is replaced.

SERVICE/REPLACEMENT
(1) Remove the air cleaner cover.
(2) Remove the air cleaner filter (Fig. 4).

CAUTION:
Do not tap the filter or immerse the filter medium in liquid to remove trapped debris.
(3) Clean filter by blowing the trapped debris from
the filter with compressed air (Fig. 5). Direct the air in the opposite direction of normal intake air flow.
Keep the air nozzle at least two inches away from
the filter.
(4) If the filter has become partially saturated with

oil,
replace the filter. Inspect the crankcase ventilat­
ing system for proper operation.
(5) Wash the air cleaner cover and body with
cleaning solvent. Wipe it dry.
(6) Install the air cleaner filter element. Attach
the cover to the body (Fig. 4).
Fig,
4
Engine
Air Oeaner—
Typical

0
- 32
LUBRICATION
AND
MAINTENANCE

•

Fig.
5 Parking Brake Ratio Lever Lubrication (2) Note any indication of brake overheating,
wheel dragging or the vehicle pulling to one side.
(3) Evaluate any performance complaints received
from the owner/operator. (4) Repair the brake system as necessary (refer to
Group 5—Brakes for additional information and ser­
vice procedures).

BODY
COMPONENT
MECHANISMS
LUBRICATION REQUIREMENTS
All operating mechanisms and linkages should be
lubricated when necessary. This will maintain ease of operation and provide protection against rust and
excessive wear. The door weatherstrip seals should
be lubricated to prolong their life as well as to im­ prove door sealing.

LUBRICANT SPECIFICATIONS
All applicable exterior and interior vehicle operat­
ing mechanisms should be:
• Inspected • Cleaned
• All the pivoting/sliding contact areas on the mech­ anisms should then be lubricated.
MOPAR®Multi-Mileage Lubricant or an equiva­
lent, should be used to lubricate the mechanisms.
The door weatherstrip seals should be lubricated
with silicone lubricant spray. Refer to the Body Lu­
bricant Specifications chart below for additional lu­
bricant applications.

LUBRICATION
(1) When necessary, lubricate the cab and cargo
box operating mechanisms with the specified lubri­
cants.

(2) Apply silicone lubricant to a cloth and wipe it
on door seals to avoid over-spray that can soil pas­
senger clothing. (3) Before applying lubricant, the component
should be wiped clean. After lubrication, any excess
lubricant should be removed.
(4) The hood latch, latch release mechanism, latch
striker and safety latch should be lubricated periodi­
cally.
(5) The door lock cylinders should be lubricated 2
times each year (preferably autumn and spring): • Spray a small amount of lock cylinder lubricant di­
rectly into the lock cylinder
• Apply a small amount to the key and insert it into
the lock cylinder • Rotate it to the locked position and then back to
the unlocked position several times
• Remove the key. Wipe the lubricant from it with a
clean cloth to avoid soiling of clothing.

TIRES
RECOMMENDED MAINTENANCE
The condition of the tires should be inspected. The
inflation pressures tested/corrected at the same time as the engine oil is changed and the oil filter is re­
placed.
The tires/wheels should be rotated periodically to
ensure even tread wear. The tires/wheels should be
rotated at the first 12 000 km (7,500-miles) interval.
Thereafter, at each 24 000 km (15,000-miles) inter­
val.
INSPECTION
Inspect the tires for excessive wear, damage. Test
the tires for the recommended inflation pressure and adjust the pressure accordingly. Refer to the tire in­
flation pressure decal located on the left door face. Also to Group 22—Tires And Wheels for tire pres­sure charts, tire replacement, and treadwear indica­

tors.

ROTATION
Tires/wheels should be rotated according to the rec­
ommended interval. The first tire/wheel rotation is
the most important for establishing the prevention of uneven tread wear. After rotation, adjust the tire in­
flation pressure to the air pressure recommended on
the decal located on the left door face.
Refer to Group 22—Tires And Wheels for the rec­
ommended method of tire/wheel rotation.

HEADLAMPS

MAINTENANCE SCHEDULE
Every six months check the headlamp beams to en­
sure that the headlamp beams are correctly posi­
tioned.

AIM
ADJUSTMENT
Refer to Group 8L—Lamps for headlamp aim ad­
justment procedures.

•

FRONT SUSPENSION
AND
AXLE
2 - 1
CONTENTS

page

FRONT SUSPENSION—2WD VEHICLES
......
7

FRONT SUSPENSION—4WD VEHICLES
14

FRONT WHEEL
ALIGNMENT
...............
3

GENERAL INFORMATION
1
page

MODEL
44
FRONT AXLE
17

MODEL
80
FRONT AXLE
49

TORQUE SPECIFICATIONS
75

GENERAL
INFORMATION

FRONT SUSPENSION—2WD VEHICLES
All two-wheel drive (2WD)
Ram
Truck
and
Ram­
charger vehicles
are
equipped with (Fig
1);

• Steering knuckles
• Stabilizer
bar
(optional) • Suspension arms
• Strut
rod

• Coil springs
• Dual-action shock absorbers
• Jounce bumpers (used
to
limit
the
travel
of the

suspension) The upper and lower suspension arms (Fig.
1)
have
replaceable bushings located
at the
inboard end.
Re­

placeable ball studs
are
located
at
the
outboard end.
The lower suspension arms
are
equipped with ten­ sion-type ball studs. The upper suspension arms also
provide
for
caster
and
camber adjustments.
STABILIZER
BAR
J9102-67

Fig. 1 Front Suspension—2WD Vehicles

FRONT SUSPENSION—4WD VEHICLES
All four-wheel drive (4WD) Ram Truck
and
Ram­
charger vehicles
are
equipped with (Fig
2);
• Leaf-springs (fixed-rate type)
• Dual-action shock absorbers • Stabilizer
bar
(optional)
• Jounce bumpers (used
to
limit
the
travel
of the

suspension)
Air-adjustable shock absorbers
are
installed
on
ve­

hicles equipped with
the
Heavy Duty Snow Plow Package with
the
Diesel engine. Refer
to
the Own­
ers Manual
for
additional information.
FRONT DRIVE AXLE The front axle
on 4WD Ram
Truck
and
Ram­
charger vehicles
has a
hypoid gear differential.
Model
44
and
60
axles consists
of
an iron center cast­
ing with axle shaft tubes extending from either side.
Ram Truck
and
Ramcharger vehicles equipped
for

standard duty 4WD operation use
the
Model
44
front
axle.
Vehicles equipped
for
heavy duty 4WD operation
use

a Model 60 front axle. The Model 60 front axle has lock­
ing hubs that must
be
engaged
for
4WD operation.
The steel cover provides
a
means
for
service with­
out removing
the
complete axle. A metal axle gear ratio identification
tag is at­

tached
to the
housing cover
via one of the
cover

bolts.
This
tag
also identifies
the
number
of
ring and
pinion gear teeth.
IDENTIFICATION Model
44 and 60
axles have
the
assembly part
number
and
gear ratio listed
on a
tag. The
tag
is at­

tached
to
the
left side
of
the housing cover (Fig.
3,
4).
Build date identification codes
on
axles
are
stamped
on
the
axle shaft tube cover side.

LUBRICANTS
Multi-purpose API
GL
5
quality hypoid gear lubri­
cant should
be
used
for
front axles. MOPAR Hypoid Gear Lubricant conforms
to
these specifications. The axle
has a
fitting
for a
vent hose used
to re­

lieve internal pressure. If the front axle
is
submerged
in
water,
the
lu­

bricant must
be
replaced immediately.

FRONT
SUSPENSION
AND
AXLE

2 - 4 FRONT SUSPENSION AND AXLE
•

I
FRONT END
|
|*?£E;
LOOSE
OR WORN
FRONT WHEEL
BEARINGS

LOOSE
C

SHOCKS

MOUNTir
WAR

SHOCK
A )RWORN

JSORBER

nIG
HARD-

E
OR
BSORBER
EXCiSSIVE
PLAY

STEERING

LINKAGE
LOOSE
OR WORN
FRONT WHEEL
BEARINGS

LOOSE
C

STEERINC
SHAFT
C
)RWORN

7
COLUMN
OUPLING
DIFFICULT

STEERING
LOOSE
OR WORN
WHEEL BEARINGS
TIRE/V
OUT OF
f
VHEEL
JA
LANCE
LOW OR UNEVEN
TIRE
AIR
PRESSURE

LO(
WHEEL B
DSE

EARINGS
LOW OR UNEVEN
TIRE AIR
PRESSURE
1vsnciEi

I
1
PULLS
TO I

I
|
ONE SIDE
j
LOOSE,
WORN
OR

GLAZED
P/S PUMP BELT LOW OR UNEVEN
TIRE PRESSURE
WHILE BR
REFE

BRAKES
AKING—

R
TO

SERVICE

LOOSE
STEERING
GEAR-TO-FRAME
RAIL BOLTS
LOOSE
STEERING

GEAR-TO-FRAME
RAIL BOLTS UNEVEN TIRE TREAD
WEAR,
OR
EX­

CESSIVELY
WORN TIRE TREAD
BROKEN
OR WEAK

REAR
SPRING LOW
POWER STEERING
FLUID
LEVEL
BROKEN
OR WEAK

REAR
SPRING
WORN

UPPER
SUSPENSION ARM BUSHINGS WORN TIE-

ROD
END

BALL
STUDS WORN TIE-

ROD
END

BALL
STUDS
SHOCK
ABSORBER

NOT FUNCTIONING
CORRECTLY
LACK
OF ASSIST
FROM POWER

STEERING
PUMP
LOOSE
OR WORN

SUSPENSION
BUSHINGS

WORN LOWER

SUSPENSION
ARM
PIVOT
BUSHINGS INCORRECT

STEERING
GEAR ADJUSTMENT
LOOSE
OR WORN

SUSPENSION
ARM
BUSHINGS
INCORRECT

STEERING
GEAR ADJUSTMENT
BALL
STUDS

REQUIRE

LUBRICATION INCORRECT FRONT
WHEEL ALIGNMENT (EITHER CASTER OR CAMBER)

LOOSE
LOWER

SUSPENSION
ARM
LOOSE
OR WORN

UPPER
SUSPENSION ARM BALL STUDS
LOOSE
OR WORN

SUSPENSION
ARM
BUSHINGS
STEERING
GEAR
LUBRICANT LEVEL LOW
WORN ISOLATOR

PAD
BETWEEN COIL
SPRING
AND

FRAME
BRACKET INCORRECT FRONT-
WHEEL ALIGNMENT (PARTICULARLY
CASTER)
INCORRECT FRONT
WHEEL ALIGNMENT INCORRECT

STEERING
GEAR ADJUSTMENT

STEERING
GEAR

MALFUNCTION
INCORRECT FRONT
WHEEL ALIGNMENT (PARTICULARLY
CASTER)

J9002-97
SUSPENSION AND STEERING
SYSTEM
DIAGNOSIS

•

BRAKES
i - 3 BRAKE DIAGNOSIS

INDEX

page

Brake
Warning Lights
3

Diagnosing
Brake Problems .................
4

Diagnosis
Procedures
3

Low
Vacuum
Switch—Diesel
Models
3
page

Master
Cylinder/Power Booster Test
5

Power
Booster
Check
Valve Test .............
6

Power
Booster
Vacuum
Test .................
6

Testing Diesel
Engine
Vacuum
Pump
Output
.... 6

DIAGNOSIS
PROCEDURES
Brake diagnosis involves determining
if the
prob­
lem
is
related
to a
mechanical, hydraulic
or
vacuum
operated component.
A
preliminary check, road test­
ing
and
component inspection
can all be
used
to de­

termine
a
problem cause. Road testing will either verify proper brake opera­
tion
or
confirm
the
existence
of a
problem. Compo­ nent inspection will,
in
most cases, identify
the
actual part causing
a
problem. The first diagnosis step
is the
preliminary check. This
involves inspecting fluid level, parking brake action,
wheel
and
tire condition, checking
for
obvious leaks
or

component damage
and
testing brake pedal response. A road test will confirm
the
existence
of a
problem.
Final diagnosis procedure involves road test analysis and
a
visual inspection
of
brake components.

BRAKE
WARNING LIGHTS
The
red
brake warning light
is
connected
to the

parking brake switch
and to the
pressure differential switch
in the
combination valve. The
red
light will illuminate when
the
parking
brakes
are
applied
or
when
a
fluid pressure drop
oc­
curs
in the
front
or
rear brake circuit.
The
light will
also illuminate
for
approximately
2-4
seconds
at en­

gine start
up.
This
is a
self test feature designed
to

check bulb
and
circuit operation each time
the en­

gine
is
started. The amber antilock light
is
connected
to the
anti-
lock rear brake hydraulic valve.
The
light will illu­
minate
if a
fault occurs within
the
antilock system.

LOW VACUUM SWITCH-DIESEL MODELS
On diesel models,
the red
brake warning light
is
also
used
to
alert
the
driver
of a low
brake booster vacuum
condition.
The
warning light
is in
circuit with
a
vacuum
warning switch mounted
on the
driver side fender
panel.
The
vacuum side
of the
switch
is
connected
to the

power brake booster.
The
electrical side
of the
switch
is
connected
to the
brake warning light. The
low
vacuum switch monitors booster vacuum
level whenever
the
engine
is
running.
If
booster vac­
uum falls below
8.5
inches vacuum
for a
minimum
of
10 seconds,
the
switch completes
the
circuit
to the

warning light causing
it to
illuminate.
The
warning light
is
designed
to
differentiate between
a low
vac­
uum condition
and a
hydraulic circuit fault.

PRELIMINARY
BRAKE CHECK
(1) Check condition
of
tires
and
wheels. Damaged
wheels
and
worn, damaged,
or
underinflated tires
can
cause pull, shudder, tramp,
and a
condition similar
to
grab.

(2)
If
complaint
was
based
on
noise when braking,
check suspension components. Jounce front
and
rear
of

vehicle
and
listen
for
noise that might
be
caused
by

loose, worn
or
damaged suspension
or
steering compo­

nents.

(3) Inspect brake fluid level
and
condition. Note
that
the
front disc brake reservoir fluid level will drop
in
proportion
to
normal lining wear. Also note
that brake fluid tends
to
darken over time. This
is normal
and
should
not be
mistaken
for
con­
tamination.
If the
fluid
is
still clear
and
free
of

foreign material,
it is OK.

(a)
If
fluid level
is
abnormally
low,
look
for
evi­
dence
of
leaks
at
calipers, wheel cylinders, brake-
lines
and
master cylinder.
(b)
If
fluid appears contaminated, drain
out a

sample.
If
fluid
is
separated into layers,
or
obvi­
ously contains
oil or a
substance other than brake
fluid,
the
system seals
and
cups will have
to be re­

placed
and the
hydraulic system flushed.
(4) Check parking brake operation. Verify free
movement
and
full release
of
cables
and
pedal. Also
note
if
vehicle
was
being operated with parking
brake partially applied.
(5) Check brake pedal operation. Verify that pedal
does
not
bind
and has
adequate free play.
If
pedal
lacks free play, check pedal
and
power booster
for be­

ing loose
or for
bind condition.
Do not
road test until
condition
is
corrected.
(6)
If
components checked appear
OK,
road test
the

vehicle.

ROAD
TESTING (1)
If
complaint involved
low
brake pedal, pump
the pedal
and
note
if the
pedal comes back
up to
nor­ mal height.
(2) Check brake pedal response with transmission
in Neutral
and
engine running. Pedal should remain
firm under steady foot pressure.

•

BRAKES
5 - 5 Disc brake rotors with excessive lateral runout or
thickness variation, or out of round brake drums are
the primary causes of pulsation. Other causes are loose
wheel bearings or calipers and worn, damaged tires.

PULL A
front pull condition could be the result of con­
taminated lining in one caliper, seized caliper piston,
binding caliper, loose caliper, loose or corroded slide

pins,
improper brakeshoes, or a damaged rotor.
A worn, damaged wheel bearing or suspension compo­
nent are further causes of pull. A damaged front tire (bruised, ply separation) can also cause pull.
A common and frequently misdiagnosed pull condi­
tion is where direction of pull changes after a few
stops.
The cause is a combination of brake drag fol­
lowed by fade at one of the brake units.
As the dragging brake overheats, efficiency is so
reduced that fade occurs. Since the opposite brake
unit is still functioning normally, its braking effect is
magnified. This causes pull to switch direction in fa­
vor of the normally functioning brake unit.
When diagnosing a change in pull condition, re­
member that pull will return to the original direction
if the dragging brake unit is allowed to cool down (and is not seriously damaged).

REAR BRAKE GRAB
OR
PULL
Rear grab or pull is usually caused by an improperly
adjusted or seized parking brake cable, contaminated
lining, bent or binding shoes and support plates, or im­
properly assembled components. This is particularly
true when only one rear wheel is involved. However,
when both rear wheels are affected, the master cylinder or proportioning valve could be at fault.

BRAKES
DO NOT
HOLD
AFTER
DRIVING
THROUGH
DEEP
WATER
PUDDLES

This condition is generally caused by water soaked
lining. If the lining is only wet, it can be dried by driv­
ing with the brakes very lightly applied for a few min­

utes.
However, if the lining is thoroughly wet and dirty,
disassembly and cleaning will be necessary.

BRAKE NOISE

Squeak/Squeal
Brake squeak or squeal may be due to linings that
are wet or contaminated with brake fluid, grease, or oil. Glazed linings and rotors with hard spots can also con­
tribute to squeak. Dirt and foreign material embedded in the brake lining can also cause squeak/squeal.
A very loud squeak or squeal is frequently a sign of
severely worn brake lining. If the lining has worn
through to the brakeshoes in spots, metal-to-metal con­
tact occurs. If the condition is allowed to continue, ro­ tors can become so scored that replacement is necessary.
Thump/Clunk

Thumping or clunk noises during braking are fre­
quently not caused by brake components. In many

cases,
such noises are caused by loose or damaged steering, suspension, or engine components. How­
ever, calipers that bind on the slide pins, or slide sur­

faces,
can generate a thump or clunk noise. Worn
out, improperly adjusted, or improperly assembled
rear brakeshoes can also produce a thump noise.

Chatter
Brake chatter is usually caused by loose or worn
components, or glazed/burnt lining. Rotors with hard
spots can also contribute to chatter. Additional
causes of chatter are out of tolerance rotors, brake
lining not securely attached to the shoes, loose wheel
bearings and contaminated brake lining.
Brakelining Contamination Brakelining contamination is usually a product of
leaking calipers or wheel cylinders, driving through
deep water puddles, or lining that has become cov­
ered with grease and grit during repair.
Wheel and
Tire
Problems Some conditions attributed to brake components
may actually be caused by a wheel or tire problem.
A damaged wheel can cause shudder, vibration and
pull. A worn or damaged tire can also cause pull.
Severely worn tires with very little tread left can
produce a grab-like condition as the tire loses and re­ covers traction. Flat-spotted tires can cause vibration and wheel
tramp and generate shudder during brake operation. A tire with internal damage such as a severe
bruise or ply separation can cause pull and vibration.

MASTER
CYLINDER/POWER BOOSTER TEST
(1) Start engine and check booster vacuum hose
connections. Hissing noise indicates a vacuum leak. Correct any leaks before proceeding. (2) Stop engine and shift transmission into Neu­
tral (3) Pump brake pedal until all vacuum reserve in
booster is depleted. (4) Press and hold brake pedal under light foot
pressure. (a) If pedal holds firm, proceed to step (5).
(b) If pedal does not hold firm and falls away,
master cylinder is faulty (internal leakage). (5) Start engine and note pedal action. (a) If pedal falls away slightly under light foot
pressure then holds firm, proceed to step (6). (b) If pedal is effort is high, or no pedal action is
discernible, power booster or vacuum check valve is
faulty. Install known good check valve and repeat steps (2) through (5).

•

BRAKES
5 - 13
COMBINATION VALVE OPERATION

METERING (HOLD-OFF) VALVE The metering valve is used to balance brake action
between the front disc and rear drum brakes. The
valve meters (holds-off) full apply pressure to the front disc brakes until the rear brakeshoes are in full
contact with the drums.
The valve is designed to maintain front brake fluid
pressure at 3-30 psi until the hold-off limit of 117 psi is reached. At this point, the metering valve opens completely permitting full fluid apply pressure to the
front disc brakes.
PRESSURE DIFFERENTIAL SWITCH AND VALVE The pressure differential switch is connected to the
brake warning light. The switch is triggered by movement of the switch valve. The purpose of the switch is to monitor fluid pressure in the separate
front/rear brake hydraulic circuits.
A decrease or loss of fluid pressure in either hy­
draulic circuit will cause the switch valve to shuttle
forward or rearward in response to a pressure differ­ ential.
Movement of the switch valve will push the switch
plunger upward. This closes the switch internal con­ tacts completing the electrical circuit to the warning light. The switch valve will remain in an actuated
position until repair restores system pressures to nor­ mal levels.

COMBINATION VALVE TESTING
TESTING METERING VALVE Metering valve operation can be checked visually
and with the aid of a helper.
Observe the metering valve stem while a helper
applies and releases the brakes. If the valve is oper­
ating correctly, the stem will extend slightly when
the brakes are applied and retract when the brakes are released.
If the valve is faulty, replace the entire combina­
tion valve as an assembly.
TESTING PRESSURE DIFFERENTIAL SWITCH (1) Have helper sit in drivers seat to observe brake
warning light and to operate brake pedal.
(2) Raise vehicle on hoist.
(3) Connect bleed hose to left or right rear wheel
cylinder. Then immerse hose end in glass jar par­
tially filled with brake fluid.
(4) Have helper press and hold brake pedal all the
way down and observe warning light.
(a) If warning light illuminates, switch is operat­
ing correctly. (b) If light fails to illuminate, check circuit fuse,
bulb and wiring. Repair as necessary and repeat test steps (3) and (4). (5) If warning light still fails to illuminate, check
brakelight and park brake switches (and wiring) with test lamp. Repair or replace parts as necessary and test differential pressure switch operation again.
(6) If warning light still does not illuminate,
switch is faulty. Replace combination valve, bleed
brakes and verify proper switch and valve operation.

COMBINATION VALVE REMOVAL/INSTALLATION
VALVE REMOVAL (1) Raise vehicle on hoist.
(2) Mark or tag brake lines connected to valve for
assembly reference.
(3) Disconnect lines at valve (Fig. 8).
(4) Disconnect wires from differential pressure
switch.
(5) Remove bolts attaching valve to frame bracket
and remove valve.
VALVE INSTALLATION (1) Mount new valve on bracket and tighten valve
and bracket screws/nuts securely.
(2) Connect brakelines to valve. Tighten fittings to
16 N*m (145 in. lbs.)
(3) Connect wires to pressure differential switch
terminal. (4) Bleed brakes.
(5) Lower vehicle and verify proper brake opera­
tion.

BRAKE
LINES AND
HOSES

BRAKE LINE AND HOSE INSPECTION Flexible rubber hose is used at both front brakes
and at the rear axle junction block. Inspect the hoses
whenever the brake system is serviced, at every en­ gine oil change, or whenever the vehicle is in for ser­

vice.

Inspect the hoses for surface cracking, scuffing, or
worn spots. Replace any brake hose immediately if
the fabric casing of the hose is exposed by cracks or abrasion.
Also check brake hose installation. Faulty installa­
tion can result in kinked, twisted hoses, or contact with the wheels and tires or other chassis compo­
nents.
All of these conditions can lead to scuffing,
cracking and eventual failure.
The steel brake lines should be inspected periodi­
cally for evidence of corrosion, twists, kinks, leaks, or
other damage. Heavily corroded lines will eventually
rust through causing leaks. In any case, corroded or damaged brake lines should be replaced.

•

BRAKES
5 - 23
VACUUM PUMP OPERATION

Vacuum pump output is transmitted to the power
brake booster through a supply hose. The hose is con­ nected to an outlet port on the pump housing and to
the check valve in the power brake booster.
Pump output ranges from a minimum of 8.5 to 25
inches vacuum. The pump rotor and vanes are rotated by the pump
drive gear. The drive gear is operated by the cam­
shaft gear. Booster vacuum level is monitored by a warning
switch (Fig. 2). The switch consists of a vacuum
chamber that measures vacuum level and a sensor in
circuit with the brake warning light. The vacuum chamber is connected to the booster
check valve by a vacuum supply hose. A wire har­
ness connects the switch sensor to the brake warning
light. If booster vacuum falls below 8.5 inches for 8-10 seconds or more, the switch sensor completes
the circuit to the warning light causing it to illumi­

nate.

VACUUM PUMP DIAGNOSIS
Vacuum pump diagnosis involves checking pump
output with a vacuum gauge. The low vacuum warn­
ing switch can also be checked with a vacuum gauge.
Refer to the diagnosis procedure in this section. A standard vacuum gauge can be used to check
pump output when necessary. Simply disconnect the
pump supply hose and connect a vacuum gauge to
the outlet port for testing purposes. Vacuum should
hold steady in a range of approximately 8.5 to 25 inches at various engine speeds.
DIAGNOSING LOW VACUUM OUTPUT CONDITION A low booster vacuum condition or a faulty low
vacuum warning switch will cause the brake warn­ ing light to illuminate. If the light does go on and in­
dicates the existence of a low vacuum condition,
check the vacuum pump, booster and warning switch
as follows:
(1) Check vacuum pump oil feed line. Verify that
line connections are secure and not leaking. If leak­ age is noted and pump is noisy, replace pump.
(2) Disconnect supply hose to booster. Connect vac­
uum gauge to this hose and run engine at various
throttle openings. Output should range from 8.5 to 25 inches vacuum. If vacuum is consistently below
8.5 inches, problem is with vacuum hoses or pump
component. If output is within specified limits, con­
tinue testing.
(3) Check booster operation as described in diagno­
sis section. Replace check valve, vacuum hoses, or
booster if necessary. However, if booster operation is correct but warning light is still on, continue testing. (4) Disconnect vacuum hose at warning switch.
Plug hose and connect hand vacuum pump to switch. (5) Start and run engine.
(6) Apply 8.5 to 9 inches of vacuum to warning
switch and observe warning light. If light goes out,
switch vacuum hose is either loose or leaking. If
light remains on, leave engine running and continue
testing.
(7) Apply 20-25 inches vacuum to switch and ob­
serve warning light operation. If light now goes out,
switch is at fault and should be replaced. If light re­
mains on, continue testing.
(8) Reconnect vacuum hoses and replace original
warning switch with known good switch. Run engine and observe warning light operation. If light is now
off, old switch is faulty. If light remains on, problem
is in wiring between switch and warning light.

VACUUM-STEERING PUMP
ASSEMBLY
REMOVAL
(1) Disconnect battery negative cable.
(2) Position drain pan under power steering pump.
(3) Disconnect vacuum and steering pump hoses
from respective pumps (Fig. 3).

Fig.
3
Vacuum
And Steering
Pump Hose
Connections

(4) Disconnect oil pressure sender wires at sender
(Fig. 4).
(5) Remove oil pressure sender (Fig. 4).
(6) Disconnect lubricating oil feed line from fitting
at underside of vacuum pump (Fig. 5).
(7) Remove lower bolt that attaches pump assem­
bly to engine block (Fig. 6).
(8) Remove bottom, inboard nut that attaches
adapter to steering pump (Fig. 6). This nut secures a
small bracket to engine block. Nut and bracket must
be removed before pump assembly can be removed from block.